An electronic device such as a cellular phone is provided with various keys as an input interface of the device. A user depresses the keys, thereby performing various operations. It is known that electronic devices have a key structure including, for example, contact switches.
For example, a key structure including contact switches described in Japanese Laid-open Patent Publication No. 2007-109486 includes a printed board module and a key module disposed on the printed board module. The printed board module includes a printed board with an electronic circuit thereon, and contact switches disposed on the printed board. The key module has, for example, a key rubber and key tops disposed on the key rubber. The key rubber is an elastic member disposed on the printed board module.
The key rubber has planar portions, supporting portions, and pushers. The planar portions are disposed opposite to the contact switches. The supporting portions support the planar portions at locations on the printed board module where the contact switches are not provided. The pushers are protrusions formed at positions on the contact switch side surfaces of the planar portions corresponding to the contact switches. The key tops are placed on the surfaces of the planar portions opposite to the surfaces on which the pushers are formed. When a user depresses any one of the key tops, the corresponding planar portion bends, the corresponding pusher depresses the corresponding contact switch, and the contact switch is thereby turned on.
In the key structure described in Japanese Laid-open Patent Publication No. 2007-109486, a front case holds the key rubber, thereby preventing the key rubber from coming off. In place of the structure disclosed in Japanese Laid-open Patent Publication No. 2007-109486, a structure may be used in which, in a case of an electronic device, a printed board module is fixed to a placement plate integral with the case, the printed board module is thereby fixed to the case, a key rubber is bonded to the printed board module without placing a front case on the key rubber, key tops are bonded to the key rubber, and the key module is thereby fixed. In this case, the thickness of the case may be reduced.
In the case where a key flexible cable is used in order to electrically connecting an electronic circuit formed on a first printed board and an electronic circuit formed on a second printed board, the key flexible cable extends from one end thereof connected to the first printed board, and is folded on the outer side of the end face of a placement plate on which the first printed board is placed, and the other end of the key flexible cable is connected to the second printed board disposed, for example, on the reverse side of the placement plate.
If another member, such as a slide module of a cellular phone, is provided in the direction in which the folded portion of the key flexible cable bends due to its own weight, the folded portion may come into contact with the other member and may be pressed toward the key rubber. In this case, the folded portion pressed by the other member presses the key rubber, and as a result, the key rubber may peel off of the printed board module.